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| 2. |
- Berner, Simon, et al.
(författare)
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Activity boost of a biomimetic oxidation catalyst by immobilization onto a gold surface
- 2006
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 244:1, s. 86-91
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Tidskriftsartikel (refereegranskat)abstract
- Thiol-functionalized cobalt porphyrins were used as a model system for investigating catalytic activity in homogeneous and heterogeneous oxidation catalysis. Self-assemble monolayers of thiol-functionalized cobalt porphyrins were prepared on a gold surface and served as heterogenous catalysts. These immoblilized molecules prevented the strong inactivation observed for their homogeneous congener. As a result, the turnover number per molecule in heterogeneous catalysis was at least 100 times higher than that of the corresponding homogeneous catalyst. It is atypical for a heterogenized catalyst to outperform its homogeneous congener. The properties of the molecular layers were characterized on the molecular level by means of X-ray photoelectorn spectroscopy (XPS) and scanning tunneling microscopy (STM). The results demonstrate that the performance of these biomimetic catalysts can be dramatically improved if the catalyst arangement can be controlled on the molecular level.
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| 3. |
- Éll, Alida H, et al.
(författare)
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Synthesis os S-Thioacetate Functionalized Cobalt(II) Porphyrins and Heterogenization on gold Surface
- 2006
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Ingår i: European Journal of Organic Chemistry. - : Wiley-VCH Verlagsgesellschaft. - 1434-193X .- 1099-0690. ; :5, s. 1193-1199
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Tidskriftsartikel (refereegranskat)abstract
- Cobalt tetraarylporphyrins 1-Co and 2-Co with thioacetate-functionalized carbon chains on the aryl groups were synthesized. The cobalt porphyrin 2-Co was immobilized on a gold surface after deprotection of the S-acetyl group. The immobilized porphyrin was studied by X-ray Photoelectron Spectroscopy (XPS) and the results suggest that a complete monolayer of porphyrins is formed.
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| 4. |
- Ledung, Greger, et al.
(författare)
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A Novel Method for Preparation of Disulfides on Silicon
- 2001
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:20, s. 6056-6058
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Tidskriftsartikel (refereegranskat)abstract
- This work describes an efficient novel method to incorporate reactive disulfide bonds onto a silica surface under mild reaction conditions. The reactive thiol groups introduced onto the silicon surface in the first reaction step will be oxidized but easily converted into highly reactive thiopyridyl groups, which can therefore easily be utilized for further organic synthesis involving thiol-containing molecules. This is done in a way that yields approximately a monolayer of reactant on the surface, thereby not adding to the roughness of the surface, of special importance, for instance, for single molecule interaction studies.
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| 5. |
- Ledung, Greger, 1974-
(författare)
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Heterogenization of a Cobalt Porphyrin Catalyst Investigated by Scanning Probe Microscopy and X-Ray Photoelectron Spectroscopy: The Effect on Catalysis of Oxidation Reactions
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Construction of advanced materials through self-assembly on the molecular level is an important route to achieve novel functionality. Self-assembly of thiols onto gold has during the last decades shown greate promise in the creation of functional nanomaterials, such as sensors or catalysts, but for many applications silicon should be a better substrate since it offers semiconducting properties and better processing abilities in addition to being cheaper. This work describes an efficient novel method to incorporate reactive disulfide bonds onto a silica surface under mild reaction conditions. The reactive thiol groups introduced onto the silica surface will be oxidized but is then converted into highly reactive thiopyridyl groups, which can easily be utilized for further organic synthesis involving thiol-containing molecules. Cobalt tetraarylporphyrins with thioacetate-functionalized carbon chains on the aryl groups were synthesized (CoTPP-L) and were used as a model system for investigating catalytic activity in homogeneous and heterogeneous oxidation catalysis. For heterogeneous catalysis CoTPP-L was immobilized onto gold surfaces through thiol-gold self-assembly, and onto silica surfaces by the above mentioned disulfide exchange method.The properties of the molecular layers were characterized on the molecular level by means of X-ray photoelectron spectroscopy (XPS) and scanning probe microscopy (SPM). The immobilization on gold surfaces took place through the formation of multiple thiolate bonds and it could be controlled by varying the preparation scheme. More thiolate bonds form if the thioacetyl protective groups of the thiol linkers are cleaved off prior to immobilization. The CoTPP-L molecules were in all cases found to form stable disordered monolayers on gold surfaces. On silica surfaces the CoTPP-L forms patchwise multilayers. The catalytic performance of the heterogenized systems (CoTPP-L immobilized onto gold or silicon wafers) was evaluated and it was found that the strong inactivation observed for their homogeneous congener was avoided. As a result, the turnover number per molecule in heterogeneous catalysis was at least 100 times higher than that of the corresponding homogeneous catalyst. It is thus demonstrated that the performance of these catalysts can be dramatically improved if the catalyst arrangement can be controlled on the molecular level. Work is ongoing to extend the system to high surface area materials.
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| 6. |
- Ledung, Greger, et al.
(författare)
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The Performance of a Biomimetic Oxidation Catalyst Immobilised on Gold and Silica Substrates
- 2007
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Ingår i: International Symposium on Relations between Homogeneous and Heterogeneous Catalysis. ; , s. 180-
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Thiol-functionalized cobalt porphyrins were used as a model system for investigating catalytic activity in homo-geneous and heterogeneous oxidation catalysis. Self-assembled monolayers of thiol-functionalized cobalt porphyrins were prepared on a gold surface and served as heterogeneous catalysts. The immobilization of the molecules prevented the strong inactivation observed for their homogeneous congener. As a result, the turnover number permolecule in heterogeneous catalysis was at least 100 times higher than that of the corresponding homogeneouscatalyst. It is atypical for a heterogenized catalyst to outperform its homogeneous congener. The properties of themolecular layers were characterized on the molecular level by means of X-ray photoelectron spectroscopy (XPS) and scanning probe microscopy (SPM). The results demonstrate that the performance of these biomimetic catalysts can be dramatically improved if the catalyst arrangement can be controlled on the molecular level. In order to further investigate the influence of the substrate on the catalytic performance, monolayers of the cobalt porphyrins were grafted onto silica surfaces. The observed catalytic activity together with the surface analytical results are interpreted in relation to the supporting substrate. Preliminary results from this investigation (silicon wafer) show that the catalytic activity is similar to that of gold substrates.
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